Route 25 (Japanese: ２５番道路Route 25) is a route in northeast Kanto, connected to Route 24 at its western end. The Sea Cottage is located at the end of the route.
Heading from west to east, Route 25 initially begins as an extension to Route 24. To the east, Route 25 comes to a maze of trees (GenerationsI, II and IV) or shrubs (Generations III and VII). Regardless of the Generation, the maze is full of Trainers ready to battle. Note that if the player loses to Cooltrainer/Ace Trainer Kevin at the end of the route, he cannot be rematched; however, since he gives the player a Nugget before the battle begins, there's no extra benefit by defeating him besides the prize money, which all Trainers give. To the northwest of the maze is a patch of grass containing wild Pokémon.
Near the east end of the maze, there is a cuttable (prior to Generation VII)/Chop Down (Generation VII) tree blocking an area that contains an item. By removing the tree, Trainers can collect a certain item. In Generations I, III, and VII, the item can also be accessed by challenging the Camper (Jr. Trainer♂ in Generation I) blocking the alternative path to a battle and making him move out of the way.
East of the maze, the route opens up to its widest point before condensing slightly near a pair of Trainers (I/III) or a single Trainer (II) and the first of two ponds near the east end of the route, known as Cerulean Cape (Japanese: ハナダのみさきHanada Cape). To the north of a land bridge between the two ponds is the Sea Cottage, the home of Pokémon expert Bill.
Route 25 continues east, turning south at the ocean shoreline and passing along a narrow strip of land between the ocean and the eastern pond. At the southern tip of the pond, the route turns west, intersecting the land bridge as it runs along the southern edge of the ponds. Just to the west of the pond, the route turns north for a yard before doubling back to the west, running along the southern edge of the route's main path as it feeds into the "express route", one way portion of Route 24. The existence of the long, narrow bypass south of Route 25 allows for quick, hassle-free travel between Cerulean Cape and its namesake city. However, due to a ledge at the southern terminus of Route 24 in Cerulean City, the reverse is not possible.
In Generations I, III, and VII, the corner connecting Routes 24 and 25 is considered a part of Route 24. In Generations II and IV, it's included with Route 25.
In Generation II, the maze was reduced in size and more Trainers were added to the west side of Route 25. This move was made due to the loss of the Nugget Bridge in Generation II. To compensate, the challenge has been moved from the bridge on Route 24 to the maze on Route 25. At the end of the maze, the reward for defeating all of the Trainers in the maze is a Nugget.
The route is nearly identical in structure to Generation III with the exception of a few minor changes. The move of the Nugget Bridge challenge to Route 25 still remains from Generation II and the territory that Route 25 occupies is the same as Generation II. The hedge that goes along the bottom of the maze is now a fence and the maze area is elevated, making the bottom half of the loop below the mountain appear at a lower level. There is also a cliff to the right of Bill's house, where Suicune can be found and caught after roaming throughout Johto and Kanto. Misty appears here as well during the evening, if Suicune is not there. The two ponds have also been replaced by one large pond, which is surrounded by a fence.